1. Field of the Invention
The present invention relates to a film forming method of forming a thin film on a substrate, such as a semiconductor wafer, a manufacturing method of a semiconductor device using the same, a film forming apparatus, and a semiconductor device,
2. Description of the Related Art
For further high integration of a semiconductor memory device, a memory cell having a pillar shape structure capable of obtaining sufficient electrostatic capacity while reducing an area occupied by a capacitor on a surface of a wafer has attracted attention. In detail, the capacitor in the memory cell includes a lower electrode having a pillar shape, a dielectric film formed on a side of the lower electrode, and an upper electrode formed on the dielectric film. By using the side of the lower electrode having the pillar shape, it is possible to secure an area for the capacitor, thereby obtaining sufficient electrostatic capacity.
Since the lower electrode having the pillar shape described above is formed to have high 2 dimensional (2D) density for high integration, the lower electrode has a high aspect ratio of, for example, a diameter of about 40 nm and a height of about 2000 nm. Accordingly, while manufacturing the memory cell, the lower electrode may be destroyed.
In order to prevent this, there have been attempts to form a support film extending in parallel to a substrate surface and supporting a plurality of lower electrodes by connecting the vicinity of tops of the lower electrodes. For example, Patent Document 1 discloses a silicon nitride film connecting tops of pillar type electrodes formed by ruthenium (Ru).
Meanwhile, according to development trends of semiconductor memory devices, for high integration, it is required to further reduce a size limit. The reducing of the size limit may, for example, deteriorate insulation characteristics of an insulation film, and in order to prevent this, an insulation material that has not been conventionally used is used. One of new materials may have, for example, a film forming temperature lower than that of previous materials. In this case, during processes after forming the insulation film, the insulation film may be deteriorated if a substrate is heated at a temperature higher than a film forming temperature of the insulation film. Accordingly, a temperature of following processes needs to be low, but in this case, for example, a stress applied to the support film described above is increased, thereby destroying a lower electrode having a pillar shape.                (Patent Document 1) Japanese Laid-Open Patent Publication No. 2010-153418        (Patent Document 2) Japanese Laid-Open Patent Publication No. 2006-287194        